Shaft collar assembly and method

ABSTRACT

Disclosed is an extended shaft collar comprising a reinforced concrete collar which extends from the surface to below a groundwater formation, providing an impenetrable barrier between the surrounding groundwater formations and the work area within the shaft. The extended shaft collar of the present invention provides a barrier to the ground and the work area of a shaft, including the prevention of contamination of shallow groundwater of the surrounding formations from the activities of the shaft, and may further be used for emergency shaft purposes. Concrete utilized in the extended collar may be comprised of conventional cements as well as specialty cements. The disclosed extended shaft collar supports a wide variety of scenarios for heavy civil construction projects, oil and gas production and mining, including subterranean oil recovery platforms and related products and services where shallow groundwater reservoirs are located.

This application includes material that is subject to copyrightprotection. The copyright owner has no objection to the facsimilereproduction by anyone of the patent disclosure, as it appears in thePatent and Trademark Office files or records, but otherwise reserves allcopyright rights whatsoever.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to: (i) Provisional United StatesPatent Application Ser. No. 62/011,647 filed on Jun. 13, 2014, entitled“Extended Shaft Collar,” and (ii) Provisional United States PatentApplication No. 62/011,662, entitled “Extended Shaft Collar forEmergency Shaft”, which provisional patent applications are commonlyassigned to the Assignee of the present invention and is herebyincorporated herein by reference in their entirety for all purposes.

TECHNICAL FIELD

The present invention relates in general to the field of heavy civilconstruction. In particular, the present invention relates to anextended length casing of a shaft collar. The disclosed systems andmethods support a wide variety of scenarios for civil construction,mining, oil recovery, and related products and services.

STATEMENT OF FEDERALLY FUNDED RESEARCH

None.

BACKGROUND OF THE DISCLOSURE

Heavy civil construction involves construction of entire engineeringprojects (e.g., highways and dams), and specialty trades, whose primaryactivity is the production of a specific component for such projects.Heavy and civil engineering construction contractors build sewers,roads, highways, bridges, tunnels, subways, and other projects.Governmental agencies, municipalities, and industries also utilize heavycivil construction for water and wastewater treatment facilities,pipeline installation, and infrastructure for water, minerals and energyproduction.

Heavy civil construction is often represented in energy productioncontexts. In addition to pipeline and water reclamation scenarios, heavycivil construction may include efforts in hydrocarbon processing andrecovery. Such applications include various secondary and tertiaryrecovery methods. Enhanced oil recovery (EOR) is a generic term fortechniques for increasing the amount of crude oil that can be extractedfrom an oil field. Enhanced oil recovery is also called improved oilrecovery or tertiary recovery (as opposed to primary and secondaryrecovery). Sometimes the term quaternary recovery is used to refer tomore advanced, speculative, EOR techniques. Using EOR, 30 to 60 percentor more of the reservoir's original oil can be extracted, compared with20 to 40 percent using primary and secondary recovery. Currentapproaches to EOR include steam flood and water flood injection andhydraulic fracturing. Other methods include gas injection, misciblesolvents, and thermal methods.

Advances in utilizing mining techniques have resulted in the renewedutilization of subterranean oil recovery platforms for enhanced oilrecovery. While previous oil mining methods have been utilized for shaleoil recovery, advances in technology now suggest subterranean oilrecovery as a viable enhanced oil recovery method.

Typically, when setting casing for a shaft associated with a drillingproject, shaft collar casing is set only for a nominal depth to ensurehole integrity is maintained. However, in situations where shaftworkings are required below shallow groundwater formations, thereremains an requirement in further ensuring the activities within theshaft are isolated from the surrounding formations.

SUMMARY OF THE DISCLOSURE

It is therefore an object of the present invention to provide anextended length shaft collar to ensure groundwater is protected frompotential inflow from the shaft in a manner not previously utilized.

It is another object of the present invention to provide an impermeablebarrier which may comprises steel or concrete, or a combination of bothto isolate the work area from the shallow water table, thus reducing thelikelihood of contamination of the water table from activitiesassociated with the subsurface oil recovery platform during theconstruction and operation of the platform.

The present invention addresses the limitations of the art by providingan extended shaft collar comprising concrete and steel casing, extendingbelow the surface and providing an impenetrable barrier between thesurrounding formations and the work area within the shaft. The concretemay be comprised of conventional Portland cements as well as specialtycements. The cement may further comprise accelerators, lightweight andheavyweight additives retarders, friction reducers, specialty materialsand other additives. Various mixing agents may also be utilized, as wellas various aggregates to ensure optimized properties in view of theproject size, depth, and location.

It is therefore an object of the present invention to provide a shaftcomprising an impermeable shaft collar extending from a surfacecontinuously underground below a groundwater formation into a competentrock formation for groundwater isolation from the shaft for anunderground drilling facility. The shaft may further comprise asurface-oriented shaft collar pad for supporting surface equipment. Theshaft collar pad is comprised of reinforced concrete and may furthersupport a hoist system, headframe, shaft, as well as utility and pipingsupports for an underground drilling facility.

It is a further object of the present invention to have an extendedshaft collar which further prevents shaft production fluids fromcontaminating a groundwater formation. The groundwater may be a shallowgroundwater formation and may be further regulated or designated asdrinking water, agricultural irrigation, or municipal supply water. Theshaft, which may be a large diameter shaft for heavy civil, mining, orsubterranean drilling purposes, may further comprise a shaft collar iscomprised of concrete, reinforced concrete, and the like. The shaftcollar may further comprise a retaining wall extending below the surfacefor supporting the extended sub-surface shaft collar. A shaft liner mayfurther connect to the shaft collar below the competent rock formation(under the water formation), wherein the shaft liner extends below theshaft collar substantially through the remaining portion of the shaft.

It is yet another object of the present invention to provide a method ofisolating subterranean shaft activities from a groundwater formation,comprising excavating a pre-determined shaft for subterraneanactivities, installing an impermeable shaft collar from the surface ofthe shaft to a competent rock formation below said groundwaterformation, placing a shaft liner impermeably connected below theinstalled shaft collar; and extending said shaft liner below the shaftcollar substantially through the remaining portion of the shaft.

This method may further comprise installing a retaining wall below theshaft collar pad and external to the extended sub-surface shaft collarand further extending below the surface for supporting the extendedsub-surface shaft collar.

It is another object of the present invention to provide an emergencyshaft comprising an impermeable shaft collar having an inner diametercomprised of a steel pipe liner extending from a surface continuouslyunderground below a groundwater formation into a competent rockformation wherein said shaft collar isolates groundwater and hazardousgas from the emergency shaft. For purposes of maintaining criticalfunctions of a subterranean work environment, the emergency shaftemploys a steel pipe liner incorporated into the inner diameter of theemergency shaft collar extending from the shaft collar into the shaftliner with the continuing shaft liner having the inner steel pipe linerextending through the remaining portion of the emergency shaft. Theemergency shaft may further serve as a ventilation shaft.

Additionally, the present invention provides extended strength andintegrity from the surface by extending the shaft collar beyond thetypical surface casing to isolate the working area of the shaft fromshallow groundwater inflows.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of thedisclosure will be apparent from the following description ofembodiments as illustrated in the accompanying drawings, in whichreference characters refer to the same parts throughout the variousviews.

The drawings are not necessarily to scale, emphasis instead being placedupon illustrating principles of the disclosure:

FIG. 1 depicts a top plan perspective view of a shaft collar andaccompanying shaft collar pad.

FIG. 2 depicts an elevation and cutaway view of a shaft collar pad andaccompanying extended collar.

FIG. 3 depicts an exploded elevation view of a shaft collar surroundingthe shaft casing.

FIG. 4 depicts a lower shaft cross-sectional view of the lower shaftreinforcement of a shaft.

FIG. 5 depicts a cross-sectional view of a cast in place shaft wall fora shaft.

FIG. 6 depicts a perspective view of a shaft collar pad constructionincluding forms and reinforcements.

FIG. 7 depicts a perspective view of a poured shaft collar.

FIG. 8 depicts a side perspective view of an emergency hoist collar padof the present invention.

FIG. 9 depicts a side perspective view of an emergency hoist airlockplatform and sheave deck, pipe section, and accompanying extendedcollar.

DETAILED DESCRIPTION OF THE DISCLOSURE

While the making and using of various embodiments of the presentinvention are discussed in detail below, it should be appreciated thatthe present invention provides many applicable inventive concepts thatcan be embodied in a wide variety of specific contexts, goods, orservices. The specific embodiments discussed herein are merelyillustrative of specific ways to make and use the disclosure and do notdelimit the scope of the disclosure.

All publications and patent applications mentioned in the specificationare indicative of the level of skill of those skilled in the art towhich this disclosure pertains. All publications and patent applicationsare herein incorporated by reference to the same extent as if eachindividual publication or patent application was specifically andindividually indicated to be incorporated by reference.

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, which form a part hereof, andwhich show, by way of illustration, specific example embodiments.Subject matter may, however, be embodied in a variety of different formsand, therefore, covered or claimed subject matter is intended to beconstrued as not being limited to any example embodiments set forthherein; example embodiments are provided merely to be illustrative.Likewise, a reasonably broad scope for claimed or covered subject matteris intended. Among other things, for example, subject matter may beembodied as methods, devices, components, or systems. The followingdetailed description is, therefore, not intended to be taken in alimiting sense.

Throughout the specification and claims, terms may have nuanced meaningssuggested or implied in context beyond an explicitly stated meaningLikewise, the phrase “in one embodiment” as used herein does notnecessarily refer to the same embodiment and the phrase “in anotherembodiment” as used herein does not necessarily refer to a differentembodiment. It is intended, for example, that claimed subject matterinclude combinations of example embodiments in whole or in part.

In general, terminology may be understood at least in part from usage incontext. For example, terms, such as “and”, “or”, or “and/or,” as usedherein may include a variety of meanings that may depend at least inpart upon the context in which such terms are used. Typically, “or” ifused to associate a list, such as A, B or C, is intended to mean A, B,and C, here used in the inclusive sense, as well as A, B or C, here usedin the exclusive sense. In addition, the term “one or more” as usedherein, depending at least in part upon context, may be used to describeany feature, structure, or characteristic in a singular sense or may beused to describe combinations of features, structures or characteristicsin a plural sense. Similarly, terms, such as “a,” “an,” or “the,” again,may be understood to convey a singular usage or to convey a pluralusage, depending at least in part upon context. In addition, the term“based on” may be understood as not necessarily intended to convey anexclusive set of factors and may, instead, allow for existence ofadditional factors not necessarily expressly described, again, dependingat least in part on context.

Subterranean oil recovery platforms, similar to traditional mining,involve the formation of shafts, bores, tunnels and the like. Often theyare specialized shafts for mining and other uses, such as subsurface oilrecovery. Shaft mining refers to the method of excavating a vertical ornear-vertical tunnel from the top down, where there is initially noaccess to the bottom. A shaft may be either vertical or inclined(between 45 and 90 degrees to the horizontal), although most modern mineshafts are vertical.

The most visible feature of a typical mine shaft is the headframe (orwinding tower, poppet head or pit head) which stands above the shaft andhouses a hoist motor. At ground level beneath and around the headframeis the shaft collar, which provides the foundation necessary to supportthe weight of the headframe and provides a means for personnel, materialand services to enter and exit the shaft. Collars are usually massivereinforced concrete structures with more than one level. If the shaft isused for mine ventilation, a plenum space or casing is incorporated intothe shaft collar to ensure the proper flow of air into and out of themine.

Beneath the shaft collar the part of the shaft which continues into theground is known as the shaft. At locations where the shaft meetshorizontal workings there is a shaft station which allows men, materialsand services to enter and exit the shaft. From the station tunnels(drifts, galleries or levels), or boreholes extend towards an ore bodyor reservoir.

A typical shaft lining performs several functions; it is first andforemost a safety feature preventing loose or unstable rock from fallinginto the shaft, then a place for shaft sets to bolt into and lastly asmooth surface to minimize resistance to airflow for ventilation. Oftensmaller shafts are designed to be rectangular with timber supports.Larger shafts are round and may be concrete lined. Shaft lining designis dependent on the geology of the rock which the shaft passes through,and some shafts may have several liners sections as may be required.Where shafts are sunk in highly competent rock there may be no lining,or a minimal installation of welded mesh and rock bolts. The material ofchoice for shaft lining is concrete which is poured behind forms.Shotcrete, fibrecrete, brick, cast iron tubing, pre-cast concretesegments have also been used. Additionally, the use of materials likebitumen and even squash balls have been required by specificcircumstances.

In circumstances involving subterranean drilling platforms, such as withunderground gravity drainage (UGD), an underground drilling facility isutilized where workers and equipment are present. These facilities maypenetrate beneath groundwater formations. Typical shaft construction mayutilize specialized liner systems to isolate the shaft operations fromthe surrounding formations. However, due to the presence of groundwaterformations, it is necessary to ensure isolation of such formations tomaintain subsurface facility habitability. Typical liners may havelimitations, including joints and grouting, which may compromiseessential groundwater isolation by allowing a leak path for waterinfiltration. In one embodiment of the present invention, a shaft collarcomprising concrete is extended from the surface an impermeable shaftcollar extending from a surface continuously underground below agroundwater formation into a competent rock formation for groundwaterisolation from the shaft to an underground drilling facility. Theextension of the collar from the surface ensures the shallow groundwatersupply is protected from the inner workings of the shaft, and in returnprotects the shaft from groundwater inflow events, as well as hazardousor combustible gases.

For the purposes of the present invention a large diameter wellbore orshaft refers to a shaft greater than or equal to 2 feet in finisheddiameter, further comprising monobores, where the diameter of the shaftis uniform from the underground facility to the surface. These types ofshafts are able to be structured in a continuous manner without therequirement for multiple casings or liners. However, the use of suchshafts require that any perforations or intervention operations beminimized to ensure the inner diameter of the shaft is not reduced to anextent shaft operations are compromised.

The term concrete in the present invention refers to a compositematerial composed of water, coarse granular material (the fine andcoarse aggregate or filler) embedded in a hard matrix of material (thecement or binder) that fills the space among the aggregate particles andglues them together. There are many types of concrete available, createdby varying the proportions of the main ingredients below. In this way orby substitution for the cementitious and aggregate phases, the finishedproduct can be tailored to its application with varying strength,density, or chemical and thermal resistance properties, as describedmore fully below.

Shotcrete is concrete (or sometimes mortar) conveyed through a hose andpneumatically projected at high velocity onto a surface, as aconstruction technique. Shotcrete is usually an all-inclusive term thatcan be used for both wet-mix and dry-mix versions. Shotcrete undergoesplacement and compaction at the same time due to the force with which itis projected from the nozzle. It can be impacted onto any type or shapeof surface, including vertical or overhead areas.

Aggregate consists of large chunks of material in a concrete mix,generally a coarse gravel or crushed rocks such as limestone, orgranite, along with finer materials such as sand.

Cement, commonly Portland cement, and other cementitious materials suchas fly ash and slag cement, serve as a binder for the aggregate. Wateris then mixed with this dry composite, which produces a semi-liquid thatworkers can shape (typically by pouring it into a form). The concretesolidifies and hardens to rock-hard strength through a chemical processcalled hydration. The water reacts with the cement, which bonds theother components together, creating a robust stone-like material.

Chemical admixtures are added to achieve varied properties. Theseingredients may speed or slow down the rate at which the concretehardens, and impart many other useful properties including increasedtensile strength and water resistance.

Reinforcements are often added to concrete. Concrete can be formulatedwith high compressive strength, but always has lower tensile strength.For this reason it is usually reinforced with materials that are strongin tension (often steel) or, with the advent of modern technology,cross-linking styrene acrylic polymers. The reinforcement is usually,though not necessarily, steel reinforcing bars (rebar) and is usuallyembedded passively in the concrete before the concrete sets. Reinforcingschemes are designed to increase tensile strength in the concrete.Modern reinforced concrete can contain varied reinforcing materials madeof steel, polymers or alternate composite material in conjunction withrebar or not. Reinforced concrete may also be permanently stressed (incompression), so as to improve the behavior of the final structure underworking loads. The most common methods of doing this are known aspre-tensioning and post-tensioning.

Mineral admixtures are also commonly utilized. The use of recycledmaterials as concrete ingredients has been gaining popularity because ofincreasingly stringent environmental legislation, and the discovery thatsuch materials often have complementary and valuable properties. Themost conspicuous of these are fly ash, a by-product of coal-fired powerplants, and silica fume, a byproduct of industrial electric arcfurnaces. The use of these materials in concrete reduces the amount ofresources required, as the ash and fume act as a cement replacement.This displaces some cement production, an energetically expensive andenvironmentally problematic process, while reducing the amount ofindustrial waste that must be disposed of.

Chemical admixtures include accelerators which speed up the hydration(hardening) of the concrete. Typical materials used are CaCl2, Ca(NO3)2and NaNO3. However, use of chlorides may cause corrosion in steelreinforcing and is prohibited in some countries, so that nitrates may befavored.

Retarders slow the hydration of concrete and are used in large ordifficult pours where partial setting before the pour is complete isundesirable. Typical polyol retarders are sugar, sucrose, sodiumgluconate, glucose, citric acid, and tartaric acid.

Air entrainments add and entrain tiny air bubbles in the concrete, whichreduces damage during freeze-thaw cycles, increasing durability.However, entrained air entails a trade off with strength, as each 1% ofair may decrease compressive strength 5%.

Plasticizers increase the workability of plastic or “fresh” concrete,allowing it be placed more easily, with less consolidating effort. Atypical plasticizer is lignosulfonate. Plasticizers can be used toreduce the water content of a concrete while maintaining workability andare sometimes called water-reducers due to this use. Such treatmentimproves its strength and durability characteristics. Superplasticizers(also called high-range water-reducers) are a class of plasticizers thathave fewer deleterious effects and can be used to increase workabilitymore than is practical with traditional plasticizers. Compounds used assuperplasticizers include sulfonated naphthalene formaldehydecondensate, sulfonated melamine formaldehyde condensate, acetoneformaldehyde condensate and polycarboxylate ethers.

Corrosion inhibitors are used to minimize the corrosion of reinforcingsteel in concrete. Bonding agents are used to create a bond between oldand new concrete (typically a type of polymer) with wide temperaturetolerance and corrosion resistance. Pumping aids improve pumpability,thicken the paste and reduce separation and bleeding.

The mix design depends on the type of structure being built, how theconcrete is mixed and delivered, and how it is placed to form thestructure. All of the above-referenced attributes may be incorporatedinto the term concrete or reinforced concrete for the purposes of thepresent invention.

It is therefore an object of the present invention to provide anextended shaft collar for purposes of protecting surrounding groundwaterfrom shaft activity. The shaft collar extends below the surface into thecompetent rock zone to form an impenetrable barrier between the shaftand the surrounding formations which may include groundwater formations.For the purpose of the present invention, a shallow groundwater supplyor groundwater formation means any groundwater formation which islocated above a subterranean facility. A groundwater formation is anunderground formation comprising groundwater. Groundwater is the waterlocated beneath the surface in soil pore spaces and in the fractures ofrock formations. A unit of rock or an unconsolidated deposit is calledan aquifer when it can yield a usable quantity of water. The depth atwhich soil pore spaces or fractures and voids in rock become completelysaturated with water is called the water table. Groundwater is rechargedfrom, and eventually flows to, the surface naturally; natural dischargeoften occurs at springs and seeps, and can form oases or wetlands.Groundwater is also often withdrawn for agricultural, municipal,personal, and industrial use by constructing and operating extractionwells.

In many jurisdictions, governing bodies impose constraints on potablewater supply for drinking water, irrigation, or other water use needs.These restrictions are placed upon operations which are drilling oroperating through a groundwater formation and require that isolation bemaintained to ensure the groundwater formation is not harmed or pollutedby the subterranean operations.

In one embodiment, a shaft is excavated, upon which a flashing ofexposed rock is provided which comprises fiber reinforced shotcrete forareas involving raveling ground. A panning and brattice cloth step maythen be applied to the bottom of the excavated shaft. Below the extendedshaft collar, a cast in place shaft lining is then set to within 50 feetof the bottom of the excavation, in order to provide protective liningfor the shaft. The shaft collar is extended from the surface below thecollar pad and retaining wall into the competent rock layer of theformation. The penetration through the shallow ground water formation isthus performed by a shaft collar which isolates the inner workings ofthe shaft from the formation inflows, and vice versa.

Turning to FIG. 1, an overhead view of the shaft borehole 105 isprovided having an inner diameter 101 comprising a concrete collar andan external retaining wall 103. At the surface of the shaft collar ashaft collar pad 102 is provided which acts as a support for surfaceequipment. The surface equipment may comprise a headframe, hoistingequipment, and supports utilities which are run in hole to service,supply, and remove, the workings from the subterranean drillingfacility. Reinforcing 104 is provided for the shaft collar 101, shaftcollar retainer wall 103 and shaft collar pad 102.

The shaft collar and accompanying shaft collar pad is designed toaccommodate the weight and support necessary for the surface equipment.The design and function of the surface equipment, and the resultingshaft collar pad which supports such equipment is a function of severalfactors using standard engineering methods associated with strength ofmaterials, constructability, and long-term operation. These factorsinclude the sizes and weights of the headframe, hoisting systems (whichmay include a personnel hoist (or skip hoist), winch hoist, utilitysupports, and the proposed weight requirements for the respectivecapacities of the above. Further, these calculations are made in lightof the service parameters of the shaft, budget, and time. Serviceparameters may include space limitations (or requirements) including thesize of the shaft based on the size of equipment which is run in hole.By way of a non-limiting example, for a subterranean drillingenvironment, the winch hoist capacity factors in the maximum weightnecessary for the equipment (such as a drilling rig) to be sendunderground to the underground facility. Further the skip hoist isfurther designed to carry a required number of personnel. It is oftenrequired that such facilities have performance requirements for emptyingand accounting the facility within a required timeframe, such as 30minutes. These regulations further account for the size of equipmentneeded, taking into account the main shaft and any existing ventilationor emergency shafts, in then calculating the size, weight and supportnecessary for the shaft collar pad.

FIG. 2 presents a side perspective view of the entire shaft collar asextended into the shaft, connecting to the shaft liner below a shallowgroundwater formation 205. The shaft collar pad 203 is extended at thesurface to accommodate surface equipment the shaft collar extendsdownward and is supported externally by the retaining wall 206 locatedexternal to the inner shaft collar. The retaining wall 206 furthersupports the extended shaft collar pad 203. The retainer wall 206further extends underground to an extent substantially supporting theshaft collar through the shallow groundwater formation 205. The shaftcollar further extends along the internal shaft 202 into a competentrock formation 204 and transitions within the competent rock formation204 into a shaft liner 207. The shaft liner 207 may employ typicalcast-in-place or pre-cast components and may further comprise an innershaft liner 209 which extends substantially the length of the shaft tothe underground drilling facility. Overbreak zones 208 in the competentrock formation are managed with various techniques described below (seeFIG. 4).

In another embodiment, the upper portion of the shaft collar as shown inFIG. 3 is extended below the ground as a support for the headframe. Aninner diameter shaft treatment 302 may comprise a steel casing, such as¾″ steel. The extended shaft collar 303 further includes reinforcement308 which extends through the shallow groundwater formation 305 into thecompetent rock formation 306. For exemplary purposes, the upper portionof the shaft collar 303 extends between the retainment wall toapproximately sixteen feet into the competent rock formation. Theextended collar then transitions to a protective casing 307 whichextends to the bottom of the shaft 301, forming an impenetrable barrier,thus preventing the transfer of products of the shaft into groundformations and, alternatively, preventing the inflow of products of theground formation into the shaft, such as groundwater.

In another embodiment, the present invention provides an impermeablebarrier of steel and concrete to isolate the work area of the shaft froma groundwater formation. In yet another embodiment, the groundwaterisolation prevents the inflow of shaft activities and produced materialsinto the shallow groundwater formations. In another embodiment, thepresent invention isolates the supply air flow from hazardous formationgases and fluids. The extended shaft collar may be used in connectionwith other water and inflow drainage capabilities necessary for removingpotential inflows present at the external portions of the shaft liner.

In one embodiment, the extended shaft collar of the present invention isutilized in heavy civil construction projects involving the formation ofa shaft. In another embodiment, the extended shaft collar is utilizedfor oil production wells. In yet another embodiment, the extended shaftcollar is utilized in subsurface oil recovery platforms and oil miningplatforms.

In a further embodiment, a method for providing an extended shaft collaris provided by having a shaft collar platform extend to competent rockformations following the excavation of a shaft wherein the collar pad isconnected to a vertical collar below the pad extending downward into theshaft. The extended shaft collar transitions to the shaft liningformation below the known groundwater formation depth. Such transitionis to shaft liner systems typical in the art, and may further includeaspects as set forth in FIG. 4, which provides a lower shaftreinforcement cross sectional view. Reinforcement bar 401 is utilized inconnection with a concrete liner which may further comprisecast-in-place concrete sections. Additional wire mesh componentry may beadded and included in connection with panning and brattice cloth 403,which may be used for stabilizing the rock formation 404 and potentialoverbreak zones 405. In situations where raveling rock is encountered,such systems comprising a panning and brattice cloth 403, welded wiremesh 406 and any required spacers 402 to separate the wire mesh from therock surface. In the event raveling rock is encountered, an initial coatof fiber-reinforced shotcrete is applied. Following the application ofthe shotcrete, if necessary, the panning and brattice cloth 403, thewelded wire mesh with spacers 402 and reinforced concrete of varioustypes are applied to complete the lining. This lining utilizes otherwater drainage features external to the inner diameter of the shaft tocollect and remove water inflows. The shaft liner continues downwardfrom the extended collar to the bottom of the shaft.

In another embodiment, the cast-in-place shaft wall of FIG. 5 may beapplied to the shaft liner. A single cast-in-place concrete liner 503may be incorporated. Spacers 501 accompanying a welded wire mesh 502 maybe utilized to hold the welded wire mesh 502 off the rock surface 506.If raveling rock is encountered from the rock formation 504, a flashcoat of shotcrete, for example, may be applied 505. The shotcrete may befiber reinforced. The shotcrete coating may further include panning andbrattice cloth coverage.

In another embodiment, the shaft collar comprises a concrete pad at thesurface for purposes of supporting surface equipment and piping supportassemblies. FIG. 6 provides a view of the shaft 601 having temporarybracing material 604 within a pad formed by forming 603 on the outeredge of the shaft collar pad and utilizing reinforcement bars 602 withinthe area where concrete is to be poured. The shaft collar then extendsbelow the pad and within a retainment wall (see FIG. 1) comprised ofconcrete. The lower extended portion of the collar extends below theretainment wall and into the competent rock. The extended collar thentransitions to the shaft lining assembly for extending throughout theremaining portion of the shaft. FIG. 7 provides a perspective view of afinished shaft collar pad 702, wherein the shaft collar 701 ispositioned at or near the center of the shaft collar pad 702. The forms703 may then be removed for completion of the construction. Thetemporary shaft supports 704 may further be removed.

In another embodiment, the shaft collar of the present invention isutilized in subterranean drilling operations involving the formation ofan emergency shaft. The extended emergency shaft collar is utilized insubsurface oil recovery platforms and oil mining platforms, includingfor emergency shafts constructed for emergency use, ventilation, andexplosion relief. In addressing such critical functions as an emergencyshaft, including ventilation, an additional steel liner is incorporatedto ensure complete liquid and gaseous isolation from the shaft inconsideration of the supply air aspects of the emergency shaft.

FIG. 8 provides a side perspective view of an exemplary emergency shaft,which may further serve as a ventilation shaft, providing airflowdownhole via surface-based ventilation equipment. The shaft 801 isprovided an inner steel casing 802, which further increases the gas andliquid impermeability to ensure critical air supply and emergencyfunction. The steel liner serves as an additional protective liner thatis vapor resistant to prevent hazardous gas infiltration (such asmethane) into the shaft, including resisting any formation water. Thisprotective liner is preferably steel, although other vapor resistantmaterials may be used provided the other materials are able to withstandthe other load and structural requirements of the shaft. The protectiveliner in a ventilation shaft (providing supply air) must further bevapor resistant to ensure the supply air remains fresh and free fromcontamination. The thickness of the steel liner is factored by strengthand corrosion needs. In one embodiment, the thickness of the steel linermay be up to two inches thick. In another embodiment, the thickness ofthe steel liner is one inch. In yet another embodiment the thickness ofthe steel liner is ¾-inch. In another embodiment, the thickness of thesteel liner is ½ A inch. In further considering the thickness of thesteel liner, the inner diameter of the shaft for functional use iscritical. Further, determinations of the corrosion resistance necessary,in the event of brackish water exposure or other harsh environments iscritical to factor in to the long term life service of the shaft.

The extended collar 803 is brought to the surface absent any expandingconcrete pad to ensure continuity in the collar for protective featuresof the emergency shaft. The emergency shaft collar pad 804 is thuspositioned external to the emergency shaft steel liner 802 and emergencyshaft collar 803. The emergency shaft pad 804 is then designed inaccordance with the supporting various surface equipment having theabove-reference criteria, and further includes emergency hoistequipment, ventilation equipment, and related headframe and airlocksystems typical of an emergency shaft. The emergency shaft 801 thencontinues downward accompanied by the extended shaft collar 803 belowthe groundwater formation 806 and into the competent rock formation 805.Because of the orientation of the emergency shaft collar pad 804external to the emergency shaft collar 803, the retainment wall 807 isthus positioned below both the emergency shaft collar 803 and emergencyshaft collar pad 804.

FIG. 9 provides another perspective view of the exemplary emergencyshaft having associated equipment supported by the emergency shaftcollar. The emergency shaft collar 907 is brought the surface asindicated in FIG. 8. The emergency collar pad 905 is truncated forpurposes of FIG. 9, but is extended as needed for accommodating theneeded hoist and ventilation equipment. A ventilation and emergencyhoist facility 903 is positioned over and supported by the emergencyshaft collar 907. The emergency hoist system comprises a hoist elevator904 for workers and equipment and related equipment, such as a wire ropesheave 901 for driving the hoist system. An explosion relief panel 902may be further provided. Worker access 908, 909, may be further providedand supported.

Those skilled in the art will recognize that the methods and systems ofthe present invention may be implemented in many manners and as such arenot to be limited by the foregoing exemplary embodiments and examples.Furthermore, the embodiments of methods presented and described asflowcharts in this disclosure are provided by way of example in order toprovide a more complete understanding of the technology. Disclosedmethods are not limited to the operations and logical flow presentedherein. Alternative embodiments are contemplated in which the order ofthe various operations is altered and in which sub-operations describedas being part of a larger operation are performed independently.

While various embodiments have been described for purposes of thisdisclosure, such embodiments should not be deemed to limit the teachingof this disclosure to those embodiments. Various changes andmodifications may be made to the elements and operations described aboveto obtain a result that remains within the scope of the systems andprocesses described in this disclosure.

What is claimed is:
 1. A shaft comprising an impermeable shaft collarextending from a surface continuously underground below a groundwaterformation into a competent rock formation for groundwater isolation fromthe shaft for an underground drilling facility.
 2. The shaft of claim 1,further comprising a surface-oriented shaft collar pad for supportingsurface equipment.
 3. The shaft of claim 2, wherein the shaft collar padis comprised of reinforced concrete.
 4. The shaft of claim 1, whereinsaid shaft collar further supports a shaft, utility and piping supportsfor the underground drilling facility.
 5. The shaft of claim 1, whereinsaid shaft collar further prevents shaft production fluids fromcontaminating a groundwater formation.
 6. The shaft of claim 1, whereinsaid shaft is a large diameter shaft.
 7. The shaft of claim 1, whereinsaid shaft collar is comprised of concrete.
 8. The shaft of claim 1,wherein said shaft collar is comprised of reinforced concrete.
 9. Theshaft of claim 1, wherein said shaft collar further comprises aretaining wall extending below the surface for supporting the extendedsub-surface shaft collar.
 10. The shaft of claim 1, wherein a shaftliner further connects to the shaft collar below the competent rockformation, said shaft liner extending below the shaft collarsubstantially through the remaining portion of the shaft.
 11. A methodof isolating subterranean shaft activities from a groundwater formation,comprising: excavating a pre-determined shaft for subterraneanactivities; installing an impermeable shaft collar from the surface ofthe shaft to a competent rock formation below said groundwaterformation; placing a shaft liner impermeably connected below theinstalled shaft collar; and extending said shaft liner below the shaftcollar substantially through the remaining portion of the shaft.
 12. Themethod of claim 11, wherein said shaft collar comprises reinforcedconcrete capable of supporting surface equipment and piping suspensionsupports.
 13. The method of claim 11, further comprising applyingflashing of supporting material to exposed raveling rock formationsprior to installing said impermeable shaft collar.
 14. The method ofclaim 11, further comprising applying flashing of supporting material toexposed raveling rock formation prior to installing the shaft linerbelow said shaft collar.
 15. The method of claim 11, wherein installingsaid shaft collar further comprises installing a shaft collar padcapable of supporting surface equipment and piping suspension supports.16. The method of claim 11, further comprising installing a retainingwall below the shaft collar pad and external to the extended sub-surfaceshaft collar and further extending below the surface for supporting theextended sub-surface shaft collar.
 17. The method of claim 11, whereinthe shaft is an emergency shaft comprising an impermeable shaft collarhaving an inner diameter comprised of a steel pipe liner extending froma surface continuously underground below a groundwater formation into acompetent rock formation wherein said shaft collar isolates groundwaterand hazardous gas from the emergency shaft.
 18. An emergency shaftcomprising an impermeable shaft collar having an inner diametercomprised of a steel pipe liner extending from a top surfacecontinuously underground below a groundwater formation into a competentrock formation wherein said shaft collar isolates groundwater andhazardous gas from the emergency shaft.
 19. The emergency shaft of claim18, wherein said steel pipe liner incorporated into the inner diameterof the shaft collar extends from the shaft collar into the shaft liner,said shaft liner having said inner steel pipe liner extending throughthe remaining portion of the emergency shaft.
 20. The emergency shaft ofclaim 1, wherein said emergency shaft further serves as a ventilationshaft.